The present invention relates generally to control systems for process control and, more particularly, to an adaptive control system that can perform control functions in either a centralized or distributed manner depending on system topology.
A centralized control system can be easy to create and maintain because all of the control logic is at a single location. However, the processing requirements can be prohibitive if the central controller is expected to implement complex control algorithms, or to execute multiple control algorithms in parallel. Similarly, the bandwidth requirements to implement complex control algorithms may be prohibitive where data needs to be acquired from many remote sensors. Another drawback is that centralized control systems lack inherent robustness due to possible failure of the centralized controller. To ensure robustness, backup controllers may be required to ensure redundancy, which can make centralized control systems expensive to implement.
A distributed control system is a more complex control system in which multiple controllers share responsibility for certain control functions. In a distributed control system, the control functions may be divided among multiple controllers. One example of this type of control system is a residential heating system having multiple heating zones with heating and cooling elements. Each zone is independently controlled to maintain the temperature within the zone at a desired temperature set point. Each of the controllers is able to set the operating mode and desired temperature for each zone based on user input.
Distributed control systems can be scaled more easily than centralized control systems by adding additional controllers to extend the functionality of the control system. Another advantage of distributed control systems is their inherent redundancy. If one controller fails, the other controllers are still available to perform the control functions of the failed controller.
Typically, a control system is designed to use either centralized control or distributed control before the system components are installed. The choice is made by analyzing the advantages of each type of control given the desired application and system configuration. In order to change from one type of control to another would require the replacement of all of the controllers and many of the controlled components. Reconfiguration of the system would therefore require that operations be halted while the new controllers and other components are installed.